MGoBlogStore Inquiry

Yesterday's discussion about the "Worst State Ever" T-shirt has invoked me to finally purchase my first hilarious garment from the MGoBlogStore.

For the T-shirts, I noticed some of the designs have two options: a $20 Gildan version and a $25 American Apparel version. Can anyone tell me how each of two brands typically run, size-wise? Larger or smaller than expected? I know there are size chart links on the FAQ page, but these can often be deceiving.